Mammalian virus systems have been studied by combined electron microscopic and biochemical methods. Polio and rhinovirus RNA fragments have been translated in vitro, and cloned in plasmids. Adenovirus early proteins have been localized in the cellular ultrastructure. Late viral protein expression has been perturbed by introduction of anti-cellular antibodies in liposomes. Newly devised computer programs have been used to analyze nucleics for homologies, secondary structures, splice sites, promoter sites and recombination sites.